The utility model provides a prevent slow -witted structure, set up in the bottom plate of intelligent power module outside with on the frame, include: prevent slow -witted post and prevent slow -witted groove, prevent slow -witted post and prevent that slow -witted groove sets up at the bottom plate of intelligent power module outside with on the frame respectively, prevent that slow -witted post and the shape and the position of preventing slow -witted groove suit. Through above -mentioned mode, the utility model provides a pair of prevent slow -witted structure, set up on the bottom plate of intelligent power module and outer frame and prevent slow -witted post and stay the groove with preventing, guarantee the bottom plate of intelligent power module and frame shelf energy and correctly assemble.